Adds a JIT based exception handling example to the examples directory.

Adds a JIT based exception handling example to the examples directory.
Both zero cost example domain specific, and C++ foreign exception handling are
shown. The example's documentation fully explains how to run the example.

Notes:

1)   The code uses an extremely simple type info model.
2)   Only a single landing pad is used per unwind edge
     (one call to llvm.eh.selector)
3)   llvm.eh.selector support for filter arguments is not given.
4)   llvm.eh.typeid.for is not used.
5)   Forced unwind behavior is not supported.
6)   Very little if any error handling is given.
7)   __attribute__((__aligned__)) is used.
8)   The code uses parts from the llvm compiler-rt project and
     the llvm Kaleidoscope example.
9)   The code has not been ported or tested on WINDOWS.
10)  The code was not tested with a cmake build.
11)  The code was tested for a debug build on 32bit X86 CentOS LINUX,
     and both a debug and release build on OS X 10.6.2 (64bit).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95723 91177308-0d34-0410-b5e6-96231b3b80d8